Detection of wheel speed sensor
(1) Check the gap between the sensor head of the wheel speed sensor and the ring gear: the front wheel should be 1.10~1.97mm, and the rear wheel should be 0.42~0.80mm.
(2) Raise the vehicle so that the wheels are off the ground.
(3) Remove the ABS wheel speed sensor harness connector and perform measurement.
(4) Rotate the wheels at a speed of 1r/s and measure the output voltage with a multimeter: the front wheels should be 190~1140mV, and the rear wheels should be higher than 650mV.
Wheel speed sensor detection procedure
When the wheel speed sensor fails, the ABS module cannot receive the correct signal output by the wheel speed sensor. At this time, a fault code will be generated, and the instrument has a fault indicator. When we suspect that a sensor is malfunctioning, we can make the following measurements to determine whether the sensor is malfunctioning and cannot output the correct signal to the ABS module.
Step 1: Measure the voltage on the plug of the wheel speed sensor. There are Hall elements, voltage regulator circuits, and operational amplifiers inside the Hall sensor, all of which need power supply and ironing. This step can directly determine whether the module has voltage Output, whether there is a problem with the power supply of the module, and whether there is a short circuit in the wire or other faults.
Step 2: To further determine whether the sensor is a two-wire Hall-type wheel speed sensor, the resistance of the sensor can be measured directly with a multimeter resistance in 2K mode. The resistance of the two-wire Hall wheel speed sensor cannot be measured. It is in an infinite state and uses a diode file. There should be a tube pressure drop of 0.3V-0.7V. If the resistance can be measured with a multimeter resistance of 2K file, the range is about 1K-1.6K, this sensor is a magnetoelectric sensor.
The third step: measuring the sensor signal, the Hall-type wheel speed sensor outputs a square wave pulse signal, which has a strong anti-interference type. Generally, the signal wire is clamped by the hook of the oscilloscope probe, and the black clamp is used for ironing the body. When the signal plate is rotated, the square wave signal waveform of 0.5V-1.5V can be seen normally.
[Note] Some cars are designed with power cables for signal output, and most cars are designed with iron wires for signal output.
Some repair shops do not have an oscilloscope, but only have a multimeter measurement method as shown in the figure below: black test lead iron, red test lead connected to the signal line, turn the signal plate by hand, the voltage of the multimeter display will fluctuate from 0.5V to 1.5V, which is normal. If there is no signal output, you should check: the signal plate (whether the signal is dirty), the sensor gap, the sensor itself, etc.
The fourth step: sensor data flow comparison method, enter the ABS module to read the sensor data flow, start the road test to observe the comparison of the sensor data flow with the other three wheel speed sensors, this method can be applied to detect the occasional failure of the sensor.
Post time: Dec-16-2021